In various commercial, institutional, or residential construction projects, it is common practice to provide a gravel fill below a poured concrete foundation wall, or to provide gravel simply for ground cover in selected locations. Many sites are easily accessible and relatively clear, and in such instances, the conveyance and spread of gravel is simply accomplished via front end loader, or via use of a “Bobcat” brand loader, or other similar machine. However, from time to time the need arises to place gravel in locations which are not easily reached from a convenient dump or staging location where gravel may be placed for temporary storage. Such sites include those having steep hillsides, or other obstacles. such as closely spaced structures. Consequently, it would be desirable to provide an efficient method for the transport of gravel from a convenient staging area to a desired placement location.
In my prior U.S. Pat. No. 6,089,795, the disclosure of which is incorporated herein in its entirety by this reference (and which was issued Jul. 18, 2000, and entitled Mobile Apparatus for Pneumatic Conveyance of Gravel or Similar Granular Material), I described an apparatus which was capable of meeting certain service requirements in order to achieve reliable conveyance of some materials. However, over the years of operating that apparatus, I found that certain types of materials are likely to result in hopper outlet plugging, or in binding or overload of screw augers, or both. Such problems have been most pronounced when attempting to convey large or irregular sized rock, since such materials often become wedged between the flytes of an auger and adjacent hopper outlet components.
Therefore, it can be appreciated that it would be desirable to provide a pneumatic rock and gravel conveyance system which combines the supply of motive air with a reliable material delivery and entrainment system, and which avoids feed hopper plugging, and which avoids auger binding or overload conditions.